This invention relates to microwave leakage detectors, and more specifically to a leakage detector which can detect microwave signals leaked from a microwave oven, or the like, when the leakage reaches above a preset level.
Microwave devices are regularly utilized for numerous applications. For example, microwave ovens are generally maintained in homes and businesses and are used for cooking and heating of foods. Also, theft prevention devices, and area protection systems utilize microwave signals for protecting an area and avoiding unauthorized intrusion. Despite the numerous utilizations of microwave energy, it has been found that microwave radiation can have detremental effect upon humans. For example, such microwave radiation can cause blindness, cause genetic damage, etc. Also, it can interfere with the proper operation of various electronic medical devices, such as heart monitors, pacemakers, etc.
In order to avoid the damaging effect of microwave energy while still permitting the beneficial use of such energy, the government has established Federal Regulations maximizing the amount of leakage permissable from microwave devices.
For example, at present microwave ovens are allowed a maximum of 5 Milliwatts of leakage after purchase. In connection with theft prevention devices, the leakage standard has been set at a maximum of a 1 milliwatt level. The typical frequencies involved in microwave ovens are the assigned frequencies of 2.45 Gc. or 915 mhz. In connection with the theft prevention devices, the standard frequency is 915 mhz.
Although manufacturers provide for guarantees as to the safe levels of microwave leakage, the amount of leakage can increase after purchase of the device. For example, a tug on the door of the microwave oven may loosen it sufficiently to increase the amount of leakage. A piece of paper, towel, or other food particle caught in the door, might keep it ajar sufficient to permit excessive leakage of microwave energy. Food buildup caught or wedged in the corner hinge area can also increase the leakage. Warping of the door after continuous use can also modify its initial positioning whereby the leakage will be far in excess of government standards.
As a result, even though at the time of purchase the level of leakage may be less than a dangerous level, continued use will modify the amount of leakage whereby it can far exceed the maximum permissable levels.
In addition, although at the present time the levels set by Federal Regulations are believed to be safe, experience with many other items such as x-rays, smoke, etc., has shown that continued testing may reveal greater dangers than initially contemplated and stricter standards may later be needed.
Individuals having microwave ovens or other microwave devices are actually unaware of the amount of leakage that occurs from the device. Such leakage can take place from the periphery of the door, around the window, from the back, the control box, or any other location on the device having an opening. The leakage can thereby go undetected and may actually reach or even exceed the government maximum allowed. Additionally, individuals who fear that the government standard may not provide sufficient control and protection, and may want to limit the amount of leakage to an extent even greater than the government standard need an indication of such leakage.
Accordingly, there is a need of a simple, efficient, inexpensive, hand held microwave leakage detector which can be set at desired levels and which will provide an alarm signal when detecting microwave leakage of a preselected frequency greater than the set level.